This invention relates generally to furnaces which utilize fuel oil or waste oil as fuel and relates, more particularly, to the means with which fuel and air is delivered to the combustion zone of such a furnace for burning.
Prior art furnaces which burn fuel oil or waste oil in a combustion zone commonly include a nozzle block assembly utilizing an atomizing nozzle through which air and oil are conducted into the combustion zone for burning and a fuel pump and air compressor for delivering fuel and air, respectively, to the nozzle. It is preferred that fuel be delivered to the combustion zone at a metered, relatively constant flow rate to ensure that a proper mixture of fuel and oil is created within the zone throughout the operation of the furnace. However, factors such as the differences in the weights of oil used in such furnaces render it difficult for common fuel pumps, such as a pump of a gear and crescent design or a diaphragm pump, to deliver fuel at a metered rate. Some prior art furnace systems utilize pressure regulating devices for oil and air pressure control, but differences in the viscosity of oil used in any one furnace system may render such regulating devices incapable of providing an accurate, metered flow rate and may require readjustment between use of oils having different viscosities.
It is an object of the present invention to provide new and improved means for delivering fuel to the combustion zone of a furnace of this class at a metered flow rate.
An additional object of the present invention is to provide a new and improved furnace system within which such fuel delivery means are utilized.
Another feature of conventional furnaces of this class relates to the preheating of oil prior to its introduction into the combustion zone. While preheating of oil may be desirable in some instances, such preheating may present problems such as the formation of deposits within the fuel line.
Accordingly, another object of the present invention is to provide a new and improved preheating means for a furnace of this class which circumvents problems commonly associated with the preheating of oil prior to its introduction into the combustion zone.
Still another object of the present invention is to provide a new and improved furnace within which such preheating means are incorporated.
Yet another feature of conventional furnaces of this class relates to the presence of oil within the nozzle upon shut-down of the furnace operation. This oil may subsequently be cooked in the nozzle, which normally remains hot for an appreciable period of time following shut-down, or may migrate or drip from the nozzle into the combustion zone or onto the flame retention head located within the zone where deposits may build up.
Accordingly, a further object of the present invention is to provide new and improved means for circumventing problems commonly associated with furnaces of the prior art related to the presence of oil within the nozzle and the nozzle block upon shut-down of the furnace operation.
A still further object of this invention is to provide such means which purges oil from the nozzle and the nozzle block upon shut-down of the furnace operation.
A yet further object of the present invention is to provide a new and improved furnace within such purging means are incorporated.